This invention relates to ablation catheters, particularly for use in ablating tissue in the chambers of a patient's heart.
The disorders that can be treated by ablating cardiac tissue include general arrhythmias, ventricular tachycardia, atrial fibrillation, atrial flutter, and Wolff-Parkinson-White Syndrome (WPW). Typically, ventricular tachycardia and WPW are treated by RF coagulation or DC discharge applied to cardiac tissue by electrode-tipped, deformable, and preset curved catheters. These catheters are of similar construction to those used in the art for electrically mapping the heart.
In order to navigate through the patient's vascular system, cardiac catheters are limited to small diameters. A typical mapping or ablation catheter has small electrodes mounted on the distal end of the catheter shaft. The electrodes can be arranged in bipolar pairs at the distal end of a catheter to ablate tissue by passing RF or DC electrical current between them through the surrounding myocardium. Alternatively, a single electrode could be disposed at the distal tip of a catheter, the single electrode being used to cause RF or DC electrical energy to pass directly through the heart tissue to a grounding plate on the surface of the patient's body.
Typically, the area of cardiac tissue that must be ablated is several times the size of the ablation region of the small electrode ablation catheters. Thus, a carpet bombing approach (i.e., ablating at many discrete sites) can be used to successfully treat cardiac disorders. This technique can lead to nonuniform ablation, as well as incomplete ablation if the ablation electrodes are not always directly in contact with myocardial tissue at each discrete site.
It is known to use a suction hole at a distal end of a catheter to engage tissue and thereby to hold the catheter in a fixed location in a patient's body while a distal ring electrode is placed in contact with tissue.
An alternative method for treating disorders in the heart is described in co-pending U.S. application Ser. No. 07/957,533, filed Oct. 5, 1992 by Daniel Bruce Fram et al., the entire disclosure of which is hereby incorporated herein in its entirety. As described in this co-pending application, a catheter having a balloon mounted on its distal end is inserted into the coronary sinus or great cardiac vein. The balloon is inflated with fluid within the coronary sinus and is heated by a heating device located within the balloon. Tissue surrounding the coronary sinus is ablated by thermal conduction from the fluid to the tissue through the wall of the balloon.